1
linux/arch/arm/mach-realview/platsmp.c
Stephen Boyd 7fa22bd546 ARM: 6993/1: platsmp: Allow secondary cpu hotplug with maxcpus=1
If an ARM system has multiple cpus in the same socket and the
kernel is booted with maxcpus=1, secondary cpus are possible but
not present due to how platform_smp_prepare_cpus() is called.
Since most typical ARM processors don't actually support physical
hotplug, initialize the present map to be equal to the possible
map in generic ARM SMP code. Also, always call
platform_smp_prepare_cpus() as long as max_cpus is non-zero (0
means no SMP) to allow platform code to do any SMP setup.

After applying this patch it's possible to boot an ARM system
with maxcpus=1 on the command line and then hotplug in secondary
cpus via sysfs. This is more in line with how x86 does things.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Kukjin Kim <kgene.kim@samsung.com>
Cc: David Brown <davidb@codeaurora.org>
Cc: Tony Lindgren <tony@atomide.com>
Cc: Srinidhi Kasagar <srinidhi.kasagar@stericsson.com>
Cc: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2011-07-07 14:45:07 +01:00

83 lines
2.1 KiB
C

/*
* linux/arch/arm/mach-realview/platsmp.c
*
* Copyright (C) 2002 ARM Ltd.
* All Rights Reserved
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/smp.h>
#include <linux/io.h>
#include <mach/hardware.h>
#include <asm/hardware/gic.h>
#include <asm/mach-types.h>
#include <asm/smp_scu.h>
#include <asm/unified.h>
#include <mach/board-eb.h>
#include <mach/board-pb11mp.h>
#include <mach/board-pbx.h>
#include "core.h"
extern void versatile_secondary_startup(void);
static void __iomem *scu_base_addr(void)
{
if (machine_is_realview_eb_mp())
return __io_address(REALVIEW_EB11MP_SCU_BASE);
else if (machine_is_realview_pb11mp())
return __io_address(REALVIEW_TC11MP_SCU_BASE);
else if (machine_is_realview_pbx() &&
(core_tile_pbx11mp() || core_tile_pbxa9mp()))
return __io_address(REALVIEW_PBX_TILE_SCU_BASE);
else
return (void __iomem *)0;
}
/*
* Initialise the CPU possible map early - this describes the CPUs
* which may be present or become present in the system.
*/
void __init smp_init_cpus(void)
{
void __iomem *scu_base = scu_base_addr();
unsigned int i, ncores;
ncores = scu_base ? scu_get_core_count(scu_base) : 1;
/* sanity check */
if (ncores > NR_CPUS) {
printk(KERN_WARNING
"Realview: no. of cores (%d) greater than configured "
"maximum of %d - clipping\n",
ncores, NR_CPUS);
ncores = NR_CPUS;
}
for (i = 0; i < ncores; i++)
set_cpu_possible(i, true);
set_smp_cross_call(gic_raise_softirq);
}
void __init platform_smp_prepare_cpus(unsigned int max_cpus)
{
scu_enable(scu_base_addr());
/*
* Write the address of secondary startup into the
* system-wide flags register. The BootMonitor waits
* until it receives a soft interrupt, and then the
* secondary CPU branches to this address.
*/
__raw_writel(BSYM(virt_to_phys(versatile_secondary_startup)),
__io_address(REALVIEW_SYS_FLAGSSET));
}